#include <iostream>
#include <math.h>
using namespace std;

double n;

int main(void)
{
    scanf("%lf", &n);
    double l = -1e4, r = 1e4, mid, tmp;
    while (r - l > 1e-8)
    {
        mid = (l + r) / 2;
        tmp = pow(mid, 3);
        if (tmp > n)
            r = mid;
        else if (tmp < n)
            l = mid;
        else
            break;
    }
    printf("%.6f", mid);
}